Optical orthogonal frequency division multiplexed communications with nonlinearity compensation

Abstract

The present invention discloses a transmitter and receiver for optical communications system, which provide compensation of the optical link nonlinearity. M-PSK modulating is used for data embedding in an optical signal in each WDM channel using orthogonal frequency division multiplexing (OFDM) technique. At the receiver side electrical output signals from a coherent optical receiver are processed digitally with the link nonlinearity compensation. It is followed by the signal conversion into frequency domain and information recovery from each subcarrier of the OFDM signal. At the transmitter side an OFDM encoder provides a correction of I and Q components of a M-PSK modulator driving signal to compensate the link nonlinearity prior to sending the optical signal to the receiver.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. provisional application 61 / 045,783 filed Apr. 17, 2008, and this application is a continuation-in-part of U.S. patent application Ser. No. 12 / 045,765 filed Mar. 11, 2008, Ser. No. 11 / 679,376 filed Feb. 27, 2007 and Ser. No. 11 / 695,920 filed Apr. 3, 2007, all of which applications are fully incorporated herein by reference.FIELD OF INVENTION[0002]This invention relates generally to optical communications systems and methods that utilize coherent detection technique, WDM M-PSK transmission and optical orthogonal frequency division multiplexing (OFDM). In particular the present invention addresses a method and system for digital compensation of nonlinearity in optical signals received via optical communication link. The invention discloses communication typically up to 100 Gb / s transmission rate that can be implemented for various information exchange structures including data transmission and video b...

AI Technical Summary

Benefits of technology

[0010]The present invention provides a system and method for optical communications with a high throughput. The system and method are disclosed for optical transmission with M-PSK modulating of an optical signal in each WDM channel using orthogonal frequency division multiplexing (OFDM) technique. The improved performance is achieved by the link non-linearity compensation at the transmitter and / or at the receiver side.

Problems solved by technology

However it is completely impractical to assure perfect control of the relative optical phase shifts between different WDM channels as they travel through their respective fibers (shown as 10a in FIG. 2 of '236) and through the MUX.

The latency of the system is quite long, it includes travel time through the link, plus processing, which is typically a few milliseconds.

The calculations show that the size of such LUT and the power consumptions make this solution impractical.

Furthermore, since the whole link is dispersive in the system described in '236, the disclosed compensation does not provide sufficient link performance.

High capacity optical signal transmission is affected by the channel nonlinearity and dispersion, which leads to the limitations in the channel capacity, transmission distance and error rates.

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